Constellation Energy has replaced its chief financial officer and named a new general counsel as the company looks to complete its merger with MidAmerican Energy Holdings Co.

Jonathan Thayer, 37, will take over as chief financial officer, replacing John Collins, the company said Tuesday. Collins will move into an advisory role to assist with the merger and other issues, and will remain as chairman of natural gas and oil company Constellation Energy Partners. Thayer was appointed treasurer in August and was previously vice president and managing director of corporate strategy and development.